Explanation: Our Galaxy is being invaded. Recent observations indicate that in
the next 100 million years, the
Sagittarius Dwarf galaxy
will move though the disk of our own
Milky Way Galaxy yet again . The
Sagittarius Dwarf (Sgr), shown as the extended irregular
shape below the Galactic Center,
is the closest of 9 known small
dwarf spheroidal galaxies that orbit our Galaxy.
Don't worry, our Galaxy is not in danger,
but no such assurances are issued for the
Sagittarius Dwarf: the intense gravitational
tidal forces might pull it apart. Oddly, however,
Sgr's orbit indicates that is has been through
our Galaxy several times before, and survived!
One possibility is that Sgr contains a great deal of
low-density dark matter that hold it together
gravitationally during these collisions.